IMPACTS OF LATE QUATERNARY FLUCTUATIONS IN WATER LEVEL ON THE ACCUMULATION OF SEDIMENTARY ORGANIC-MATTER IN WALKER-LAKE, NEVADA

Walker Lake, a terminal saline lake in western Nevada, has experienced major fluctuations in its water level due to changes in regional climate and river diversions during the late Quaternary. Change in the degree of preservation of sediment organic matter has accompanied the lake level fluctuations, and changes in the biotic sources of organic matter to the lake sediments have occurred in response to the climate changes and water diversions. The record of these events has been studied using organic matter C/N ratios and carbon isotope contents and employing molecular compositions of geolipids extracted from the sediment. Modern sediments contain mostly lake-derived organic matter which has been altered by microbial reworking. Decreases in the degree of preservation of organic matter indicate lake lowstands. Increases in the proportion of land-plant components in sediment organic matter also indicate lowstand conditions. © 1990.